3D Semiconductor Metal Layer Stack for Thermal-Safe Layer Transfer
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Solution Overview
Problem
In 3D stacked integrated circuits, heat removal is challenging due to high power density and thermal resistance, with existing methods like liquid coolant passage and thermal vias facing limitations, and techniques like hydrogen exfoliating implantation causing lattice damage requiring high-temperature annealing, which can deform underlying devices.
Innovation Solution
Incorporating a heat spreading and conducting material layer between sensitive metal interconnects and the annealing region, using optical annealing to repair lattice damage at lower temperatures, and employing a shield/heat sink layer with enhanced horizontal heat conductivity to manage heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hydrogen exfoliating implantation is used to form detaching layer, then layer transfer is enabled, but crystal lattice structure is damaged requiring high-temperature annealing
Solution Approach 1:
A sacrificial intermediate layer (e.g., silicon dioxide or silicon nitride) is introduced between the donor and acceptor wafers. This intermediate layer enables layer transfer through mechanical cleavage or chemical etching without requiring hydrogen ion implantation, thus avoiding crystal lattice damage while maintaining the ability to transfer semiconductor layers between substrates
Solution Approach 2:
The harmful hydrogen ion implantation step is extracted and removed from the process flow. Instead, a clean separation method using the sacrificial intermediate layer is employed, which achieves the same layer transfer function without introducing lattice damage that would require subsequent high-temperature annealing
2Stability of the object's composition
If high-temperature annealing is performed to repair lattice damage, then crystal structure is recovered, but underlying metal interconnects and devices are damaged
Solution Approach 1:
A thermal barrier layer (e.g., silicon dioxide or silicon nitride) is positioned between the annealing region and the underlying metal interconnects. This layer acts as a thermal insulator, allowing the top semiconductor layer to be annealed at high temperatures to repair lattice damage while protecting the sensitive metal interconnects and devices below from thermal damage
Solution Approach 2:
The structure is segmented into distinct thermal zones using the thermal barrier layer, allowing independent temperature control: the upper semiconductor layer can be heated to annealing temperatures (e.g., 900-1100°C) while the lower metal interconnect region remains at safe temperatures, enabling selective thermal processing
3Productivity
If 3D stacking is implemented to reduce wire lengths, then transistor density improves, but heat removal becomes challenging
Solution Approach 1:
Heat removal paths are extended into the vertical dimension through through-silicon vias (TSVs) that conduct heat from upper device layers down to heat sink structures on the substrate. This three-dimensional thermal management architecture allows efficient heat evacuation from high-density stacked transistors by utilizing the vertical stacking direction for thermal conduction
4Area of stationary object
If metal layers are placed close to semiconductor layers for compact design, then device area is reduced, but metal migration and contamination risks increase
Solution Approach 1:
A protective barrier layer (e.g., silicon dioxide, silicon nitride, or titanium nitride) is positioned between the metal interconnect layers and the semiconductor device layers. This barrier layer prevents metal atoms from migrating into the semiconductor during processing and operation, and also prevents contamination during subsequent processing steps, thereby maintaining metal interconnect stability in compact designs
Solution Approach 2:
The structure employs composite material layers combining different functions: conductive metal layers for electrical interconnection, insulating dielectric layers for electrical isolation, and barrier layers for contamination prevention. This multi-material composite approach enables compact integration while maintaining the reliability of metal interconnects through the protective barrier layer
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively removes heat from 3D ICs without damaging metal interconnects, enables defect-free crystalline layer formation at lower temperatures, and improves the yield and reliability of 3D semiconductor devices by reducing thermal stress on sensitive layers.
Implementation Method 1
shield/heat sink layer with enhanced horizontal heat conductivity
Implementation Method 2
optical annealing to repair lattice damage at lower temperatures
Data Source
AI summary
A semiconductor device, the device including: a first silicon layer including a first single crystal silicon layer; a plurality of first transistors each including a single crystal channel; a first metal layer disposed over the plurality of first transistors; a second metal layer disposed over the first metal layer; a third metal layer disposed over the second metal layer; a second level including a plurality of second transistors, the second level disposed over the third metal layer; a fourth metal layer disposed over the second level; a fifth metal layer disposed over the fourth metal layer; a via disposed through the second level, where at least one of the plurality of second transistors includes a metal gate, where an average thickness of the fifth metal layer is greater than an average thickness of the third metal layer by at least 50%; and at least one Electrostatic discharge (“ESD”) structure.